How do I send signal to all processes in a cgroup?

kill $(/tasks ) works, but looks clumsy, produces a warning if cgroup is empty and may hit command line length limit. pkill -F does not accept cgroup tasks file as a valid pidfile. There seems to be no dedicated tool like cgkill. What should I use (apart from a fully fledged containers like LXC) to make forced cgroup termination more reliable and self-documenting? Ideally it should also do the { SIGTERM, then wait, then freeze, then SIGKILL, then thaw } routine.